Hydraulic cylinder with self-locking end cap

ABSTRACT

A self-locking, internally threaded end cap for a hydraulic cylinder comprises a tool engaging aperture formed through a sidewall thereof adapted for tightening the end cap in place on the cylinder. A plastic patch completely circumvents the aperture, internally of the end cap, for sealing and locking purposes. The patch is formed by sprinkling a powdered plastic, such as nylon, through a hole formed in a template and onto heated portions of the threads.

United States Patent 1 Goade et al.

[ 1 HYDRAULIC CYLINDER WITH SELF-LOCKING END CAP [75] Inventors: JamesC. Goade, Joliet; John A.

McDonald, Morton; Herschel M. Williamson, Joliet, all of I11.

[73] Assignee: Caterpillar Tractor Co., Peoria, Ill.

[22] Filed: June 28, 1971 [21] Appl. No.: 157,534

[ Aug. 7, 1973 103,348 5/1870 Ligon 15l/l4.5 3,294,139 12/1966Derziosi.. 2,087,185 7/1937 Dillon 3,488,666 l/l970 Podell 151/7 FOREIGNPATENTS OR APPLICATIONS 803,489 l/1957 Great Britain l5l/7 662,8631/1949 Great Britain 151]? Primary Examiner-Charles J. Myhre AssistantExaminer-R. 1-1. Lazarus Attorney-Charles M. Fryer et a1.

[57] ABSTRACT A self-locking, internally threaded end cap for ahydraulic cylinder comprises a tool engaging aperture formed through asidewall thereof adapted for tightening the end cap in place-on thecylinder. A plastic patch completely circumvents the aperture,internally of the end cap, for sealing and locking purposes. The patchis formed by sprinkling a powdered plastic, such as nylon, through ahole formed in a template and onto heated portions of the threads.

3 Claims, 3 Drawing Figures HYDRAULIC CYLINDER WITH SELF-LOCKING END CAPBACKGROUND OF THE INVENTION This invention generally relates toself-locking, threaded members or fasteners and more particularlyrelates to a self-locking end cap for a hydraulic cylinder.

The inherent memory and related physical characteristics of certainplastics has encouraged their use in patch form on self-locking,threaded fasteners. Nylon, for example, may be bonded to selected threadportions of a male or female fastener to provide a reusable and highlyefficient thread lock means.

SUMMARY AND OBJECTS OF THE INVENTION An object of the present inventionis to provide an economical self-locking threaded member which isadapted for expeditious installation and removal. The member iscylindrical and has a tool engaging aperture formed through a sidewallthereof and a deformable and reusable plastic patch bonded to selectedportions of the threads. The patch circumvents the aperture to sealagainst entry of foreign particles therethrough and to perform a lockingfunction when the fastener is threaded onto a mating second member. Inthe preferred embodiment of this invention, the members respectivelyconstitute the end cap and housing of a hy draulic cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERREDEMBODIMENT Although the self-locking member or fastener illustrated inFIGS. 1-3 constitutes an internally threaded, cylindrical end cap of adouble-acting hydraulic cylinder, it should be understood that themember can take other forms. For example, a self-locking member may havethreads formed externally thereon for threaded engagement with aninternally threaded second member or could comprise a polygonal sideinternally threaded nut.

The end cap, symmetrically disposed on a longitudinal axis X thereof(FIG. 2), is internally threaded at 11 to engage with external threads12 formed on a housing or second member I3 of the cylinder. In thisapplication, the end cap holds a tubular combined bearing and sealinggland 14 in place within the housing. In particular, an annular land 15is formed on the gland to be locked in place between an endof thehousing and the end cap.

The housing has a piston and rod assembly reciprocally mountedtherein,including a rod l6.which extends through a bearing bore 17 formed in thegland. One end of the rod has an eye 18 formed thereon which is adaptedfor attachment to a work implement (not shown). The other end of the rodis secured to a piston (not shown) which is reciprocally mounted in abore 19 of the housing.

Hydraulic fluid may be alternately introduced into and exhausted from aclosed chamber defined on each side of the piston, via lines 20 and 21,in a conventional manner. One end of the housing has an apertured flange22 formed thereon adapted for attachment to the frame of an earthworkingmachine, for example. A spanner wrench or the like (not shown) isadapted to engage a work tool receiving aperture 23, formed through asidewall of the end cap transversely of axis X (FIG. 3), to tighten orloosen the cap on the housing.

The self-locking of the end cap on the housing is achieved by means of agenerally circular plastic patch 24 bonded to confined portions ofunmodified and uninterrupted threads ll, closely adjacent to aperture23, (FIGS. 2 and 3). The plastic material used therefor can be selectedfrom any of the well-known reusable and thermoplastic resins or epoxies(e.g., nylon) which will exhibit the desired self-locking and memorycharacteristics when suitably sized and composed. US. Pat.

Nos. 2,741,288; 3,061,455; 3,093,177; 3,294,139; 3,498,352; 3,554,258and 3,568,746 disclose typical examples of such materials and methodsfor applying same to threaded fasteners. p

The plastic patch preferably completely circumvents aperture 23 and hassufficient radial thickness relative to axis X (FIG. 3) so that inaddition to the self-locking function, it will also serve as a seal toprevent the egress of dirt, water and other foreign materials into thethreaded area. In particular, the patch blocks the'portions of threads12 which intersect the aperture to prevent the materials from spiralingalong the thread cavities and into the interior of cap 10. Ingress ofsuch materials into the cap would induce corrosion and rusting of themetallic threads thereby making it difficult, if not impossible, toremove the cap from the cylinder.

One method for applying the patch to the end cap is as follows: The endcap is first cleaned, such as shotblasting; The circumferential areaaround aperture 23, whereat the plastic patch is to be applied, ispreferably coated with a thin coat of primer (e.g., an epoxy resin),

which is compatible with the plastic material utilized,

to insure a good bond between the plastic and the metal threads; The endcap is heated to a temperature in the approximate range of from 400 to500F.; A curved template (not shown), 'having a hole formed therethroughcorresponding to the size of patch 24 and slightly larger than aperture23, is then placed in position in the endcapto expose aperture 23centrally thereof; A powdered plastic (e.g., nylon) is preferablysprinkled onto the heatedthread portions, exposed by the aperture formedin the template, to at least partially melt same; and the finished endcap is cooled resulting in the semi-donut shaped patch configurationillustrated in FIGS. 2 and 3.

What is claimed is: v

I. A hydraulic cylinder disposed ona longitudinal axis thereofcomprising,

an end cap having uninterrupted spiral threads formed internally thereonto extend in the direction of and about said longitudinal axis,

means forming a work tool receiving aperture through a sidewall of saidend cap, transversely of said longitudinal axis,- and through a portionof said threads, and

whereat the thread portions of said housing intersect said aperture.

2. The invention of claim 1 further comprising a tubular gland, mountedin said cylinder, including an annular land disposed in locked positionbetween an end of said housing and said end cap.

3. The invention of claim 2 further comprising a piston and rodassembly, reciprocally mounted in said housing, having a rod thereofextending through said tubular gland and in sealing relationshiptherewith.

1. A hydraulic cylinder disposed on a longitudinal axis thereofcomprising, an end cap having uninterrupted spiral threads formedinternally thereon to extend in the direction of and about saidlongitudinal axis, means forming a work tool receiving aperture througha sidewall of said end cap, transversely of said longitudinal axis, andthrough a portion of said threads, and a generally circular patch ofplastic material, having selflocking characteristics, bonded andconfined to portions of said threads closely adjacent to said apertureto completely circumvent said aperture and a housing having said end capthreadedly mounted thereon, said plastic patch having a sufficientradial thickness relative to said longitudinal axis to be deformed bythe threaded engagement between said end cap and said housing to resistrelative turning movement therebetween and to seal the area whereat thethread portions of said housing intersect said aperture.
 2. Theinvention of claim 1 further comprising a tubular gland, mounted in saidcylinder, including an annular land disposed in locked position betweenan end of said housing and said end cap.
 3. The invention of claim 2further comprising a piston and rod assembly, reciprocally mounted insaid housing, having a rod thereof extending through said tubular glandand in sealing relationship therewith.